The heart of the early Spitfires was the Rolls Royce Merlin engine in its various Mk’s. Probably the best Spitfire version was the Merlin 61 fitted to the MkIX with its two stage super charger giving better high altitude performance over the Merlin XX then fitted to the Spit MkV.

The Merlin had started life in the mid 30’s when RR, as a private venture, for sore the need to replace its Kestrel engine used in the by-planes of the time. The target they set themselves was a V12 engine producing up to 1000hp with total reliability! The prototype was so successful that Sydney Camm on seeing it immediately ordered a re-design of his Hurricane fighter (then on the drawing board) to accommodate the new engine. Most people will know the basic history from this point with regard the Spitfire and the Mustang and later the Lancaster and Mosquito to name but a few. During my research I did find this one short article that I feel sums up just what a superb engine the Merlin is. Historic Flying of Duxford UK who restore Spitfires and Hurricanes to the highest standards has chosen Universal Airmotive of Chicago as its preferred supplier for engine restoration. This is what they say about rebuilding the Merlin:

“The Rolls Royce or Packard built Rolls Royce Merlin is one of the finest piston engines ever conceived. Employing technology fifty years ahead of its time, the Merlin engine is a true fighter thoroughbred.

The Merlin is still state of the art in piston engine technology, far beyond any automotive technology today. Rolls Royce’s goal was to create an engine that produced as much horsepower as its weight and displacement, and do so at high altitudes. This goal was achieved through the development of exotic alloys and metallurgy, and through advanced design techniques.
After a distinguished service history during the Second World War, the Rolls Royce Merlin continued in commercial service in Britain and Canada into the late fifties. These engines, most notably the six and seven hundred series, were the subject of intense testing and modification until as late as 1960.

Commercial operators logged more time on their Merlins than the military operators did by far, and consequently they had problems military over haulers never had to deal with. In addition, it was not cost effective to replace every part when it was worn past service limits, so Rolls Royce developed thousands of repair schemes and modifications to salvage otherwise unserviceable parts, and to extend the running life of parts within the engine. These repair schemes and modifications were the product of enormous amounts of engineering, development and testing before approval by the British Air Ministry.

Warbird engines are now starting to accumulate the same time in service that commercial engines of the mid-fifties saw, making major rework necessary on some components. Some overhaulers are inserting automotive technology into the Merlin in order to meet this need. Sometimes with fair results, sometimes with disastrous results, but never with the same reliability as Rolls Royce parts and repairs, which still surpass most automotive technology today. No overhauler can expend the resources to engineer and test changes to the Merlin to the same level as they were tested by Rolls Royce, and most of the modifications and repair schemes that Rolls Royce developed for the commercial operators can be used to maintain the military engines with perfectly reliable results. No guesswork, and no lost aircraft due to questionable engineering or some overlooked variable. Rolls Royce did the testing on the ground so you won’t have to in the air.

At Universal Airmotive Ltd. we install no automotive technology into our Merlin engines, only Rolls Royce repair schemes and modifications coupled with genuine Rolls Royce and Packard parts. We have the only set of genuine Rolls Royce overhaul tools in existence, not just the tools to disassemble and reassemble the engine, but tools to rework every component as well. “

Historic Flying is confident that Universal Airmotive is the leading authority on the rebuild and restoration of Rolls Royce and Packard Merlin and Griffon engines and that the engines they deliver fully live up to our rebuild philosophy.

There are two main options when building a 1:48 Spit with an exposed engine, the CMK kit which we are looking at here and the Aires kit that forms a useful benchmark.

This particular kit (CMK) is designed to be used with the Hasegawa Spitfire MkIX, as is the very similar Aires resin kit. The Kit is made up of approximately 40 resin pieces attached to their pouring reservoirs. Also supplied is a photo etch sheet of approximately 20 pieces from Eduard. These resin pieces are incredibly delicate and great care has to be taken to separate them from their reservoir blocks without breaking them .The supplied CMK instructions are good and clear and are printed in Czech and English although you will have to do your own research as regard colours.

I am not reviewing the Hasegawa Spit MkIX here except to say it’s an easy build. I will point out though that some may not realise that the kit gives you the option to make either a Mk IX or a clipped wing MkXVI although this is not mentioned on the box.

You will of course need your spitfire kit 90% assembled and with the front cut off as per my photo and the instructions. Removing the front section of the two fuselage halves is the first step. You will need to remove the front sections along the panel lines and I suggest you cut to leave the lines showing and then trim back to them. I used a combination of a photo etched model saw from “Airwaves” and a super sharp surgical scalpel .At this point I chose to “open the door” on the side of the cockpit as well! Next you will have to fit the front engine mount /bulkhead, this fits in very nicely. Make sure you have it fitted nice and square as it’s the datum for everything else. Next step is the belly panel under the engine that is “dove tailed “ in to the underneath of the fuselage below the leading edge of the wing.. Once again its important to get the positioning right and I strongly suggest you tape it in position and offer up the engine to check its position. The main engine bearer is part of the belly pan so make sure the engine bearer meets up with the engine mounts cast into the engine block. The key to this whole assembly is the relation of the forward bulk head to the belly pan as both have engine contact points, get this right and your almost home and dry!

Also note that the instructions at this stage show parts “pur14” the front engine bearers mounted up the wrong way. I also found it impossible to fit the engine after mounting part  “pur13” so be careful to dry fit all parts and use a certain amount of common sense J (note: not supplied). No mention of part “pur21” is made but it is of course the coolant header tank and goes above the reduction gear on the front of the engine.

Once you have fitted the engine you can move on to the photo etch parts that form the framework around the engine to which the outer panels would be fitted. The Aires kit provides this framework in two parts basically, left and right. The CMK kit supplies the frame in many parts and they give you a template to assemble these parts into a left and right assembly (which does not fit). Once you have assembled this frame you will have to cut and trim to fit.

I used the Std RAF camouflage of the time and Eagle strike decals to represent Flt Lt Otto Smik’s aircraft of 312Sqn, 1944.

 Neither the Aires nor the CMK engine kit is aimed at the beginner. That said the CMK is a lot more user friendly because the engine is given an exact mounting position by the inclusion of the belly pan and it’s moulded in main engine bearer. The Aires set is a lot more comprehensive in detail but because you don’t get the belly pan as a structural piece, the engine is located on the very fragile engine bearers, slung from the engine bulkhead. This means that the exact positioning of the engine is very dependant on the angle you mount the bearers. Both kits will give you a very displayable model. The CMK kit requires you to carefully follow the instructions and an intermediate model maker should have no real problems. The Aires kit is more detailed and gives a better finished product but you will need to be a competent model maker and you will need to be able to improvise because some bits are so fragile just removing them from their poring blokes can end in disaster. Put simply, if you regard yourself as a 5/10 model maker go for the CMK, if you are 7/10 go for the Aires set. Unfortunately, I am probably a 6/10 J
 Either of these engine kits will mean your finished model will be a £45.00 ($80.00) kit, is it worth it ? In my opinion, yes if you can pull it off. Both these kits have given me pleasure as finished models on my shelf (and that’s a first) They are both just nice things to own !!

One final point. It would, with a little work, be possible to fit the engine panels to the CMK kit but it would prove a major head ache should you wish to do this for the Aires kit as they simply don’t fit (too small)

I built both of these kits “from the box” and used just the instructions and a few personal photos as reference. If you choose to go the Aires route, you will need some photo reference because of the extra detail ,the basic line drawn instructions are a little inadequate.